Multifocal lens and method of making the same



p r V H. w. HILL 2,173,651

MULTIFbQAL LENS AND METHOD OF MAKING THE SAME V Fi1qd fan. 21,- 1937 Y is Sheets-Sheet 1 JRA H5111 111111? F151? fliflfllimfilim INV ORV Hneev .H L

BY 95 m ATTORNE Sept. 19, 1939.

Filed Jan. 21, 1937 3 Sheets-Sheet 2 HEM FIEIJZF HlilF INVENTOR HHEEY N HILL Y H. w. HILL 2,173,651

MULTIFOCAL LENS AND METHOD OF MAKING THE SAHE Filed Jan. 21, 193'? f Sheejs-Shast 3 INVENTOR fine/2X N HILL Patented Sept. 19, 1939 m'nro'car. mus

mm W. mu. Southbrldgalhhoa,

v American Optical 1 Company,

a voluntary association of Manchu-1 Ham, "*9 Y aosignor to Southbrldge,

Application w :1, 1937. Serial in. 121,602

2 Claims. (cuss-s4) This invention relates to multifocal lenses and to methods for making the same. More particularly the invention relates to the making of trifocal lenses. 1

An object of the invention is to facilitate mak ing the reading portion and the intermediate vision portion of such shapes as are best accommodated to the requirements of the user.

In the accompanying drawings which illustrate my invention, Fig. I is a view in elevation of one form of trifocal lens embodying my invention;

Fig. II is a sectional view on the line II-II of Fig. I;

Fig. III is a view in elevation of a two-part button for use in making the reading portion of the trifocal lens;

Fig. IV is a sectional view on the line IV- of Fig. III;

Fig. 'V is a view in elevation of the minor portion which serves to provide the intermediate distance portion of the finished trifocal lens;

Fig. VI is a section on the line VI--VI of Fig. V;

Fig. VII is a sectional view of a composite of the minor portion and the two-part button;

Fig. VIII is a similar sectional view of this composite after a spherical surface has been formed on the button side of the composite;

Fig. IX is a view in elevation of the major portion of the blank with a countersink recess formed in one side thereof;

Fig. X is a sectional view showing the composite fused in this recess.

Figs. XI and XII are views similar to Figs. I and II of another embodiment of my invention;

FignXHI is a view in elevation of one two-part button having a countersink recess formed therein; i

Fig. XIV two two-part buttons, the second'button being fused in the countersink recess of the first;

Fig. XV is a sectional view of the composite after a-spherical surface has been formed on the side where the second button is fused;

Fig. XVI is a sectional view of this composite fused in a countersink recess in a major blank portion;

Figs. XVII and XVIII are views similar to Figs. XI and XII showing still another embodiment of my invention; I

Fig. XIX is a view in elevation of a two-part button having a countersink recess formed in the face thereof; f k

Fig. x is a sectional view on the 1inexx -xx of .Fig. and illustrating the way in which is a sectional view of a composite of i one part of the button is carried the other pa t:

Fig. XXI is a sectional view through a second two-part button, one side of which has been provided' with a spherical surface contrageneric to the countersink recess of the other button;

Fig; XXII is a view in elevation showing the two two-part buttons fused together;

Fig. XXIII is a sectional view on the line XXIII-XXI1I of Fig. XXII; and

Fig. XIHV shows a major portion of glass with the composite of the two two-part buttons'fused in a countersink therein.

, Of the three embodiments of my invention illustrated in thedrawin'gs, the first incurs mini.-,

the intermediate portion and the major portion of the lens. Of the three forms, the first is in general the simplest to manufacture and the second is somewhat simpler to manufacture than the third.

Referring to the first sheet of drawings, the triable volume of production of multifocal lenses,

some of the parts may be manufactured and kept in stock.

For instance, the two-part button illustrated in Figs. III and IV and made up of the parts 6 and I is of a type familiar to those engaged in the manufacture of multifocallensesr Glass for the part 6 is selected of an index of refraction suitable for the reading segment of the finished lens. We here adopt the common designation for this segment 2, and it will be-understood that the same may have a higher or lower index of refraction than the intermediate portion 4, according to the requirements of user. The glass for the part I is selected of an index of refraction sensiblythe. same as the minor portion 8 shown in Figs. V and VI. r

This minor portion 8 is'provided with a countersink recess 9. The button 6, 1 is provided with a surface substantially contrageneric to the oountersink recess 9, (see Fig. IV) and the two part button is fused or in other suitable manner secured in the latter (see Fig. VII). The major blank portion II is also provided with a countersink recess l2 for receiving the composite of the minor portion 8 and the two-part button 6, 1. The composite is provided on its button side with a surface contrageneric to the countersink tion 8 fused to the major portion II. The countersink recess i2 remains as a substantially continuous surface of separation between glasses of dissimilar indices of refraction. The segment 2 is embedded in the face of the minor portion 8 which lies against this recess l2. Moreover, this segment 2 has a shoulder it along at least a portion of its edge, which shoulder is buried in the minor portion 8.

This rough blank is ground and polished according to customary practice for forming a continuous optical surface' on the segment side of the blank, herein the convex side, and for forming a continuous optical surface of the required power on the opposed side of the blank, herein the concave side, so as to complete the lens. One of these continuous optical surfaces will generally be placed on the blank at the factory and the other will in general be formed by the dispenser at the time the prescription is filled,

Th modification of my invention illustrated on the second sheet of drawings is in principle generally the same as the first modification. The major blank portion l5 has a countersink recess therein along an edge of which is a shoulder [8 against which abuts the intermediate portion ll of the trifocal lens. The reading segment l8 lies embedded in the intermediate portion ll between that portion and the major portion l5.

sink recess, this button having a part 2| 0! glass of an index of refraction suitable for the intermediate field of the trlfocal lens and a part 22' of glass of sensibly the same index of refraction as the major portion IS. The countersink recess 23 is mostly formed in the part 2|, although no injury is brought about by allowing it to overlap slightly the part 22. A second button is prepared with a spherical surface contrageneric to the countersink recess 23. This buttonhas a part 25 of glass of an index of refraction suitable for e segment I! and a part 26 of glass of an ind x refraction sensibly the same as that of the part 2|. The two two-part buttons are accured together as by a fusing process, the composite thus produced being shown in Fig. XIV. The major blank portion 21 is provided with a countersink recess 28 as in the first embodiment; and the composite above referred to is surfaced to produce a spherical surface on the side thereof carrying the: two-part button 2- 26. An are 29 is marked on 'Fig. XIV to indicate this spherical I surface, because we mu t be numeral '41.

taken to insure that none of the glass 28 be left overlapping the glass 22. In other words, the are 29 must pass through the surface of separation between the parts 2| and 22 of the larger two-part button.

The composite thus surfaced is fused in the countersink recess 2' to obtainthe rough blank shown in Fig. XVI. It will be noted that the segment is is in finished form. It will also be noted that the countersink recess 28 is not continuous after the last mentioned fusing but ends at the shoulder I0. This is because the Blass 22 is of sensibly the same index of refraction as the glass 21 and becomes substantially integral therewith in fusing.

The rough blank is formed with a continuous optical surface on the segment side of the blank, herein the convexside, and this surface is indicated by the arc ii in Fig. XVI. The lens is completed byforming on the opposed side of the blank a continuous optical -surface indicated by the arc 32. The first, indicated by the arc ll, is generally formed at the factory, while the second, indicated by the numeral 32 is generally formed at the time, the prescription is filled.

This embodiment of my invention has the advantage that the optical axes of the several fields of the trifocal lens may be so selected that the shoulders I! and I6 produce substantially no J p A third embodiment of my invention is illustrated on the third sheet of drawings, the finished lens being quite similar to the lens illustrated in Figs. XI and XII; but the method of manufacture being somewhat different. The major portion II is again formed with a countersink recess along a portion at least of whose edge is a shoulder 80.

Although the method of manufacture of this embodiment permits this shoulder 36 to be continuous about the entire intermediate portion of the trifocal, this is in general objectionable so that usually the shoulder 2' will extend along only a portion of the periphery of the intermediate field 3'I. The segment 38 is disposed as in the second embodiment and is likewise provided with a buried shoulder 39 as, in that embodiment.

The two-part button which is provided with a countersink recess is illustrated in Figs. XIX and XX, the countersink recess being indicated by the The part 42 of the button, which is to form the intermediate field 31, is of glass of index of refraction suitable for that field. This part 42 is received within an opening 43 in a carrier portion 44. In other words, I produce a socket 43 having walls of substantial depth in a selected location'withina carrier portion of glass 44. The segment 42 is shaped to accurately fit within the recess or socket 42 and is secured therein as by fusing. The carrier portion 44 is of glass of sensibly the sameindex of refraction as that 'of the major blank portion 35. The countersink recess 4| is then formed in one side of this twopart button. The second two-part button shown in Fig. XXI is then produced in similar fashion as the first two-part button. This button has a part 48 of glass of index-of refraction suitable for the segment 38, and a part 41 of glass of sensibly the sameinde'x of refraction as that of the part 42 of the first button. The two-part button 40, 41 is provided on one side with a spherical surface contrageneric to the countersink 4|.

The countersink 4| may overlap the carrier poras tofacilitate insertionofan ma a. ment, for instance, thescgment 10. It will be noted, however-.Ythatthelcsa this overlaps-the carrier-portion the srnallerfithe v I U I wall ina. minor pieceof lens 4 medium of a-difierent index-of'refraction than amount of's saswhichmusth from the carrierportion l4. of the two two-part buttons-is then provide'd with a. spherical surface contrageneric to the countersink recess ll n the major blank portion Ii. An arc 8| indicates the spherical surface produced on the compodte. This are must pass through the bounding walls of the socket or recess 0, since nowhere should theglass l1 overlap the glass 44 after this spherical surface (as indicated by the arc Ill has been produced on the composite. The composite is fused in the countersink recess 4! to produce the rough blank illustrated in Fig. XXIV.

As shown by Fig. XXIV the segment 38 know in finished condition and has the buried shoulder 8! above referred to. The only portion of the glass 41 now remaining is in abutting relation with this shoulder 3!. Since the glass 41 is of substantially the same index of refraction as that of the glass 42 it has become substantially integral therewith in the course of the fusing step. The glass H is of substantially the same index of refraction as the glass of the major blank portion 5. and has likewise become substantially integral as indicated by the cross-hatching in Fig. XXIV.

The finished lens shown in Figs. XVII and XVIII is produced by forming a continuous optical surface on the segment side of the blank. as indicated bythe are 52 in Fig. XXIV, and by forming a continuous optical surface on the opposite side of the blank. In the present embodiment side of the lens so as to form a knife edge along the greater portion of the lower side of the intermediate segment 31. The same is true in producing the spherical surface indicated by the arc 5| in Fig. XXIII. in that the greater portion of the lower side of the segment 38 should be finished to a knife-like edge. Such a knife-like edge is practically invisible to the wearer of the lens.

The second form of my invention illustrated in Figs. XI to XVI inclusive makes it possible to obtain a knife-like edge along the entire lower outline of both 'the segment l8 and the intermediate field th s knife-like edge in each case extending from the corner down around the bottom of the field or segment and up to the opposite corner. With the form of my invention shown in Figs. XVII to XXIV inclusive, the shoulder ex-. tends across the top of the segment 38 or intermediate field 31 and may extend any desired distance" down the sides. Both embodimen s lend themselves to considerable variation in the placing of the reading segment relative to the intermediate field and furthermore to considerable variation in the dimensions and shapes of the segment and intermediate field.

While I have illustrated and described certain embodiments of my invention it will be understood that my invention may be otherwise embodied and practiced within the scope of the following claims:

I claim: 1. In a method of making a multifocal lens the steps consisting of forming a inamajo'r piece of lens medium of one indexof refraction, producing a composite button. an opening having a conthemajor' piece, securinga segnientof lens mediunr'of a different indexof refraction thanzthe minor piece and different thanthe major piece in the opening in said minor piece andin abutting I of sensibly the same index of refraction as said major piece of lens medium and to a diameter greater than the diameter of the opening in said minor piece of lens medium, securing apiece of lens medium of sensibly the same index of refraction as the minor piece in said opening and in abutting relation with the bounding wall of said opening, forming a countersink in a side surface of said last named assembled pieces of lens medium substantially to the radius of curve.- ture of the surface formed on the minor and segment pieces of lens medium, securing said composite button in said countersink, forming a surface on the side of said joined pieces of lens medium having the composite button thereon to substantially the same radius of curvature as the curve of the countersink in the major piece of lens medium with the line of said surface passing substantially through the point of intersection of the continuous curve, on said joined minor and segment pieces of lens medium, with the bounding wall of said joined pieces of lens medium, securing said composite structure in the countersink in the major piece of lens medium and forming a curved surface on the side of said major piece of lens medium having the composite structure thereon and simultaneously reducing the lower side of said piece of lens mediumof sensibly the same index of refraction as the minor piece to a knifelike edge, said countersink curve in the major piece of lens medium being continuous and the said segment and minor pieces of lens medium both being located to one side of said countersink curve with the segment embedded in the minor piece of lens medium.

2. In a method of making a multii'ocal lens, the steps consisting of forming a countersink in a major piece of lens medium of one index of refraction, producing a composite button by forming an opening having a continuous bounding wall in a minor piece of lens medium of a different index of refraction than the major piece, securing a segment of lens medium of a different index of refraction than the minor piece and different than the major piece in the opening in said minor piece and in abutting relation with the r. all of said opening, surfacing one side of said joined minor and segment pieces of lens medium with a continuous curve which intersects said bounding wall and to a radius of curvature which controls in part the resultant power of the field formed by said segment, forming an opening with a continuous bounding wall in another piece of lens medium of sensibly the same index of refraction as said major piece of lens medium and to a diameter greater than the lens medium, securing a piece of lens medium of sensibly the same index of refraction as the minor piece in saidopening and in abutting relation with the bounding wall ofsaid opening, forming a countersink in a side surface of said last named assembled pieces of lens medium substantially to the radius of curvature of the surface formed on the minor and segment pieces of lens medium, securing said composite button in said countersink, forming a surface on the side of said joined pieces of lens medium having the composite button thereon to substantially the same radius of curvature as the curve of the countersink in the major piece of lens medium with the line of said surface passim substantially through the point of intersection of the continuous curve, on said joined minor and segdiameter of the opening in said minor pieoe'of.

ment piecu of lens medium. with the bounding wall of said joined pieces of lens medium, securing said composite structure in the countersink in the major piece of lens medium, forming a curved surface onthe side of said major piece of lensmediumhavingtheoomposite structure thereon and simultaneously reducing the lower side of said piece of lens medium of sensibly the same index of refraction as the minor piece to a knifelike edge, said countersink curve in the major piece of lens medium being continuous and the said segment and minor pieces of lens medium both being located to one side of said countersink curve with the segment embedded in the minor piece of lens medium and forming a curved surface on the opposite side of said major piece of lens medium to complete the lens.

HARRY W. HILL. 

